CBSE Class 10 Science 2015 Term I Set 1

Question : 16 of 36

Marks: +1, -0

Find the current drawn from the battery by the network of four resistors shown in the figure.

Solution:

Resultant resistance of

R_1, R_2

and

R_3

R^{'}\;=R_1+R_2+R_3

\;=10+10+10=30 Ω

Resultant resistance of the circuit :

\;{1}/{R}\;=\;{1}/{R^{'}}+\;{1}/{R_4}

\;=\;{1}/{30}+\;{1}/{10}=\;{1+3}/{30}=\;{4}/{30}

R\;=\;{30}/{4}=\;{15}/{2}=7.5

Here,

{\V}=3 {\V}, {\I}=

?
By Ohm's law,

⇒ {\V}\;= {\IR}

\; {\I}\;=\;{ {\V}}/{ {\R}}=\;{3}/{7.5}=\;{30}/{75}=0.4 {\A}

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